Caries or periodontal diseases are thought to be infectious diseases caused by bacteria present in dental plaques and it is known that the removal of dental plaques is highly important for the health of oral cavities. However, dental plaques are not easy to identify by the naked eye and it is difficult to confirm their attachment site and extent thereof precisely.
Accordingly, dental plaques are generally stained with dental-plaque staining agents, which contain dyes, to reveal their locations in order to uncover the attached dental plaques. Among the dental-plaque staining agents which have conventionally been commercially available, although tar dyes such as Red No. 3 (erythrosine), Red No. 104 (phloxine), and Red No. 105 (rose bengal) have been often used as dye components, these dental-plaque staining agents stain not only dental plaques red but also gums, oral mucosa, lips, or the like indiscriminately. Since the red stains are not easy to remove, cannot be removed sufficiently by normal toothbrushing using a toothbrush, and remain on interdental parts, gums, lips, or the like, there was a problem of causing an uncomfortable feeling.
A yellow pigment of beni-koji and turmeric are known as staining agents used for other purposes.
The abovementioned yellow pigment of beni-koji is a yellow pigment obtained from the culture medium of beni-koji mold, which belongs to Ascomycota, and is used in fish paste, fish eggs, jellies, frozen desserts, or the like for coloring purposes. As for intraoral use, a composition for the oral cavity, which contains cationic antiseptics that prevent water-soluble dyes to bleach, is disclosed (Patent document 1).
The aforementioned turmeric is a perennial plant, which belongs to Zingiberaceae, and the rhizome extract containing curcumin has been used not only as a pigment, which is simply added to food products or the like, but also as a herbal medicine such as a cholagogue or an aromatic stomachic for many years. In addition, it is attracting attention in recent years since it is said to be effective in suppressing skin-, gastric-, and colon cancers, preventing complications of liver damage and diabetes, and improving antiallergic action. On the other hand, as for use in the oral cavity, prevention of oral-cavity cancer by healing the precancerous lesion of the oral cavity (Patent document 2), antimicrobial activity against bacteria which cause periodontal diseases (Patent document 3), prevention of gingivitis and periodontitis (Patent document 4), an antioxidant (Patent document 5), or the like have been disclosed. However, these are not intended to stain dental plaques.
In addition, techniques to detect dental plaques by staining them with dyes or fluorescent agents such as Red No. 3 (erythrosine), Red No. 213 (rhodamine B), Yellow No. 201 (fluorescein), and chlorophyll and then irradiating specific light onto them have been disclosed (Patent document 6, Patent document 7, Patent document 8, Patent document 9, Patent document 10). Methods such as these using dyes and light concomitantly require dyes to not only be excited by the light and fluoresce but also to attach themselves firmly to dental plaques. However, since currently known fluorescent agents such as chlorophyll or fluorescein do not stain dental plaques sufficiently, there was a problem in reliability of detection results of dental plaques.
With such a background, demands for a method to detect dental plaques with high precision have been increasing.
Furthermore, instruments to irradiate light in oral cavities (Patent document 11, Patent document 12) and a method to irradiate specific light to detect caries (Patent document 13) have been disclosed. Additionally, techniques to detect dental plaques solely due to light by irradiating specific light (Patent document 14, Patent document 15) have been disclosed.
However, from initial dental plaques which attach to the tooth surface to dental plaques which turned into dental calculi, dental plaques are known to change their structures and inhabiting bacterial species with time and thus, the above techniques to detect dental plaques solely by specific light have not been possible to detect dental plaques which are in the initial phase of their formation.    [Patent document 1] Japanese Unexamined Patent Application, First Publication No. Hei 10-120539    [Patent document 2] Japanese Laid-Open Patent Application No. 2002-20278    [Patent document 3] Japanese Unexamined Patent Application, First Publication No. Hei 4-5222    [Patent document 4] Japanese Patent Publication No. 3314978    [Patent document 5] Japanese Laid-Open Patent Application No. 2001-322923    [Patent document 6] U.S. Pat. No. 3,309,274    [Patent document 7] U.S. Pat. No. 3,711,700    [Patent document 8] U.S. Pat. No. 4,292,664    [Patent document 9] U.S. Pat. No. 4,266,535    [Patent document 10] U.S. Pat. No. 5,957,687    [Patent document 11] Japanese Laid-Open Patent Application No. 2002-85351    [Patent document 12] Japanese Utility Model Registration No. 3066528    [Patent document 13] Japanese Patent Publication No. 1944198    [Patent document 14] Published Japanese translation No. 2002-515276 of PCT International Publication    [Patent document 15] Japanese Laid-Open Patent Application No. 2004-65994